In physics, something is "black" if it absorbs lots of the light that hits it - an ideal "black body" for instance absorbs all the light that hits it.
Being black, in this sense, does not stop something from also glowing,

For an object to be black in color, it need only absorb light in the visible spectrum.

Dark Matter (DM) by comparison, does not interact with light at all, light just passes right through, and it is a label to be used until we can figure out what is going on.
The article is about this sort of DM and how it may be interacting with the regular matter in Neutron stars to result in the statistical lack of neutron stars in the galactic core.
It goes on to tell you what sort of stuff this sort of DM would be consistent with. If the theory is right, and that's a big "if", then it narrows down the field of possibilities.

DM is unlikely to explain where all the regular antimatter ended up - why would anti-DM gravitating to anti-matter do anything special?
More likely a similar mechanism gave rise to the asymmetry of both types of matter.

The article is very speculative right now - it is not even clear how you'd be able to tell if a pulsar were dying due to dark matter or not and there are other possibilities for the lack of pulsars in the galactic core.

Staff: Mentor

That isn't a mystery; it all got annihilated by matter as the early universe expanded and cooled. The mystery is why there was a small amount of matter left over; ordinarily we would expect matter and antimatter to be created in equal quantities at the end of the inflation era, so the annihilation process would have left only radiation behind. However, the discovery of CP violations in the weak interaction provided a mechanism that could produced a slight asymmetry between matter and antimatter; this is currently believed to be the reason why our universe today contains matter but (practically) no antimatter.

As I understand the observable gravitational effects of dark matter, the speculation introduced in the referenced article ignores much about these observations. I am sorry I cannot readily cite a source reference, but a major part of the dark matter in the universe is all around and through galactic clusters, not just in the galaxies. The behavior of the motion of galaxies in clusters requires this to be so.

What I find puzzling about this idea is that there is an implication that there is a much higher concentration of DM near the galaxy core than the average in the halo. From recent dialogs in other threads, I have come to understand that in order for a DM particle to change its orbit relative to a central mass from one of large geometry to smaller, it has to get rid of its energy. Also, unlike baryonic matter, this is very unlikely since DM doesn't have interactions that can create photons to radiate away the orbital energy, as happens with baryonic matter.

... in order for a DM particle to change its orbit relative to a central mass from one of large geometry to smaller, it has to get rid of its energy. ...

I think the answer to this could be that not all orbits are perfectly circular. in fact that would probably be rare.
An eliptical orbit can have the orbiting object sometimes closer and sometimes further from the COM without needing to lose energy.
It only has to travel faster when nearer to the COM, and only gravity is involved.

An eliptical orbit can have the orbiting object sometimes closer and sometimes further from the COM without needing to lose energy.
It only has to travel faster when nearer to the COM, and only gravity is involved.

Hi rootone:

The problem with a DM particle P in large elliptical orbit falling onto a neutron star (NS) is that P will have to hit the surface of NS, and that is a very tiny target. Also, the angle at which P hits NS may have further limiting constraints. AFAIK, no one has done any analysis about this possibility, calculating the fraction of the DM halo that might hit and be captured by the NS, that is, not just pass through a portion of the NS and continue its orbit.